How to use the plivo.RestAPI function in plivo

var enableSip = config.get(C.SIP_ENABLED);
      var sipUri = config.get(C.SIP_URI);
      var sipUsername = config.get(C.SIP_USERNAME);
      var sipPassword = config.get(C.SIP_PASSWORD);
      var sipRequireGoogleAuth = config.get(C.SIP_REQUIRE_GOOGLE_AUTH);
      var plivoAuthId = config.get(C.PLIVO_AUTH_ID);
      var plivoAuthToken = config.get(C.PLIVO_AUTH_TOKEN);
      var googleId = config.get(C.GOOGLE_CLIENT_ID);
      var googleHostedDomain = config.get(C.GOOGLE_HOSTED_DOMAIN);
      if (sipRequireGoogleAuth) {
        googleAuth = new GoogleAuth.EnabledGoogleAuthStrategy(googleId, googleHostedDomain);
      } else {
        googleAuth = new GoogleAuth.DisabledGoogleAuthStategy();
      }
      if (enableSip) {
        plivoClient = plivo.RestAPI({
          authId: plivoAuthId,
          authToken: plivoAuthToken,
        });
      }
      // This isn't strictly necessary... but since we're using promises all over the place, it
      // makes sense. The _P are just a promisified version of the methods. We could have
      // overwritten the original methods but this way we make it explicit. That's also why we're
      // breaking camelCase here, to make it patent to the reader that those aren't standard
      // methods of the API.
      ['startArchive', 'stopArchive', 'getArchive', 'listArchives', 'deleteArchive', 'dial',
        'forceDisconnect']
        .forEach(method => otInstance[method + '_P'] = promisify(otInstance[method])); // eslint-disable-line no-return-assign

      var maxSessionAge = config.get(C.OPENTOK_MAX_SESSION_AGE);
      var maxSessionAgeMs = maxSessionAge * 24 * 60 * 60 * 1000;
      var chromeExtId = config.get(C.CHROME_EXTENSION_ID);

function getPlivo () {
  return Plivo.RestAPI({
    authId: PLIVO_ID,
    authToken: PLIVO_TOKEN
  });
}

PlivoBase.prototype.getPlivoAPI = function() {
    var api = plivo.RestAPI({
        authId: this.config.plivo.authId,
        authToken: this.config.plivo.authToken,
    });
    return api;
};